Sounds good to me. In theory, collapsing Earths 1 (Arrowverse), 2 (Zoom), 3 (Jay Garrick's Flash), "S" (Supergirl) and the 90s Flash Earth into a single Earth could work with a LOT of hand-waving. But, I think it's simpler, more convenient and potentially much more fun and compelling from a story point of view to keep them all separate.
Supergirl now has Lynda Carter on their roster. Imagine an episode where Supergirl ends up on an Earth where Wonder Woman has been a superhero for hundreds of years (to explain Carter's real life aging) and has achieved all sorts of wonderful (pun intended) things. Imagine what a source of inspiration that could be for Kara. Or there's hundreds of other possibilities for all four DC TV shows.
We already know that the Flash will be travelling to Gorilla City on Earth 2. That's just one example of the creative teams still being able to play with all of the interesting ideas provided by the Multiverse. Not to mention potentially the most interesting of all - the DC Movie universe/s co-existing with the four DC TV shows. I doubt it would ever happen, but imagine if they did have a scene of Ezra Miller's Flash in the Speedforce and Grant Gustin's Flash goes speeding by. How awesome would that be!
I think that's a lot better than bring Superman, Supergirl, Martian Manhunter, etc into the Arrowverse.